Question: What is the volume of a cylinder with base radius $4$ and height $9$ ? $4$ $9$
Solution: The area of the base is simply the area of a circle: $\pi r^2 = \pi \cdot 4^2 = 16 \pi$ The volume of the cylinder is the area of the base times the height: $B \cdot h = 16\pi \cdot 9 = 144\pi$.